36 GEOLOGICAL MEMOIRS. 



several birds, and other animals still undetermined. An atlas and 

 jaw, however, sent by M. Trogon to Prof. Pictet, of Geneva, were 

 ascertained by this eminent palaeontologist to belong to Cervus eury- 

 ceros*. The length of the atlas is 0*265 metre, and its breadth 

 0088 metre; both differing only by y-^Q- from the measurements 

 stated by Cuvier. [Count M.] 



On the occurrence of Thallophytes in the Cretaceous Strata 

 ©/"Aix-la-Chapelle atid Maestricht. By Dr. Debey. 



[Proceed. Imp. Acad. Sciences, Vienna, July 16, 1857.] 



As far as our present information extends, the Alffce, the lowest form 

 of vegetables, occur in primaeval marine deposits in a proportion far 

 inferior to that which may be inferred from the predominance of sea 

 over land in those remote ages. Fossil Alffce are generally small and 

 of very delicate structure. Gigantic forms, such as the living Les- 

 sonia /uscescens, Macrocystis i^yriferuy and others, measuring from 

 700 to 800 feet in length, and equalling a man's arm in thickness, 

 seem to have been wanting in the extinct marine floras. Moreover, 

 many fossil plants originally ranked among the Alga, have been 

 proved recently not to belong to this class, or, at least, to be of a 

 dubious character. The forms that have been named Confervites, 

 Caulerjntes, Chondrites, Cylindrites, Keckia, Encoelites,Muensteria'\, 

 &c. are still very doubtful, and indeed may never have belonged to 

 any organized being. Other forms, belonging to quite different sub- 

 divisions of vegetables far higher in the organic scale, have been 

 erroneously ranked among the Algce, as, for instance, several species 

 of Caulerpites, recently raised to the rank of Coniferae. 



By the investigation of the Cretaceous flora of Aix-la-Chapelle, 

 although it be richer than all other coeval floras taken together, the 

 proportion of the Algce to the other vegetable forms of the Cre- 

 taceous period is lowered to 9pjj per cent. The class of Lichenes is 

 represented in the Aix-la-Chapelle strata by only one form, answer- 

 ing to the genus Opegrapha. Some forms undoubtedly belonging 

 to the Fungi — a class never before ascertained to have existed during 

 the Chalk-period — have been lately met with. Since Prof. Goep- 

 pert's striking discovery of a foliar Fungus (^Exstipulites Neesi) on 

 the fronds of a Fern from the Carboniferous strata, there is nothing 

 surprising in the occurrence of similar forms in more recent deposits. 

 Five species of Xylomites have been found in the Lias ; at least forty 

 species of different genera have been observed in Tertiaries, and 

 especially in amber. They are generally foliar Fungi, occurring on 

 Insects or on fossil wood. Distinct remains of two species of Fungi 

 analogous to the existing genera (Ecidium and Himantia have been 

 found on the foliar impressions of Dryophyllum, a fossil genus of 

 ProteacecB. A third species, similar to a Sphcerium, was met with 



* See Bibliotlieque Universelle, Mai 1857. 



t Also Scolitkus : Quart. Journ. Geol. Soc. vol. xiii. p. 204, — Edit. 



